#include "builtin.h"
#include "cache.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "tag.h"

static const char * const fmt_merge_msg_usage[] = {
        "git fmt-merge-msg [--log|--no-log] [--file <file>]",
        NULL
};

static int merge_summary;

static int fmt_merge_msg_config(const char *key, const char *value, void *cb)
{
        static int found_merge_log = 0;
        if (!strcmp("merge.log", key)) {
                found_merge_log = 1;
                merge_summary = git_config_bool(key, value);
        }
        if (!found_merge_log && !strcmp("merge.summary", key))
                merge_summary = git_config_bool(key, value);
        return 0;
}

struct list {
        char **list;
        void **payload;
        unsigned nr, alloc;
};

static void append_to_list(struct list *list, char *value, void *payload)
{
        if (list->nr == list->alloc) {
                list->alloc += 32;
                list->list = xrealloc(list->list, sizeof(char *) * list->alloc);
                list->payload = xrealloc(list->payload,
                                sizeof(char *) * list->alloc);
        }
        list->payload[list->nr] = payload;
        list->list[list->nr++] = value;
}

static int find_in_list(struct list *list, char *value)
{
        int i;

        for (i = 0; i < list->nr; i++)
                if (!strcmp(list->list[i], value))
                        return i;

        return -1;
}

static void free_list(struct list *list)
{
        int i;

        if (list->alloc == 0)
                return;

        for (i = 0; i < list->nr; i++) {
                free(list->list[i]);
                free(list->payload[i]);
        }
        free(list->list);
        free(list->payload);
        list->nr = list->alloc = 0;
}

struct src_data {
        struct list branch, tag, r_branch, generic;
        int head_status;
};

static struct list srcs = { NULL, NULL, 0, 0};
static struct list origins = { NULL, NULL, 0, 0};

static int handle_line(char *line)
{
        int i, len = strlen(line);
        unsigned char *sha1;
        char *src, *origin;
        struct src_data *src_data;
        int pulling_head = 0;

        if (len < 43 || line[40] != '\t')
                return 1;

        if (!prefixcmp(line + 41, "not-for-merge"))
                return 0;

        if (line[41] != '\t')
                return 2;

        line[40] = 0;
        sha1 = xmalloc(20);
        i = get_sha1(line, sha1);
        line[40] = '\t';
        if (i)
                return 3;

        if (line[len - 1] == '\n')
                line[len - 1] = 0;
        line += 42;

        src = strstr(line, " of ");
        if (src) {
                *src = 0;
                src += 4;
                pulling_head = 0;
        } else {
                src = line;
                pulling_head = 1;
        }

        i = find_in_list(&srcs, src);
        if (i < 0) {
                i = srcs.nr;
                append_to_list(&srcs, xstrdup(src),
                                xcalloc(1, sizeof(struct src_data)));
        }
        src_data = srcs.payload[i];

        if (pulling_head) {
                origin = xstrdup(src);
                src_data->head_status |= 1;
        } else if (!prefixcmp(line, "branch ")) {
                origin = xstrdup(line + 7);
                append_to_list(&src_data->branch, origin, NULL);
                src_data->head_status |= 2;
        } else if (!prefixcmp(line, "tag ")) {
                origin = line;
                append_to_list(&src_data->tag, xstrdup(origin + 4), NULL);
                src_data->head_status |= 2;
        } else if (!prefixcmp(line, "remote branch ")) {
                origin = xstrdup(line + 14);
                append_to_list(&src_data->r_branch, origin, NULL);
                src_data->head_status |= 2;
        } else {
                origin = xstrdup(src);
                append_to_list(&src_data->generic, xstrdup(line), NULL);
                src_data->head_status |= 2;
        }

        if (!strcmp(".", src) || !strcmp(src, origin)) {
                int len = strlen(origin);
                if (origin[0] == '\'' && origin[len - 1] == '\'') {
                        origin = xmemdupz(origin + 1, len - 2);
                } else {
                        origin = xstrdup(origin);
                }
        } else {
                char *new_origin = xmalloc(strlen(origin) + strlen(src) + 5);
                sprintf(new_origin, "%s of %s", origin, src);
                origin = new_origin;
        }
        append_to_list(&origins, origin, sha1);
        return 0;
}

static void print_joined(const char *singular, const char *plural,
                struct list *list, struct strbuf *out)
{
        if (list->nr == 0)
                return;
        if (list->nr == 1) {
                strbuf_addf(out, "%s%s", singular, list->list[0]);
        } else {
                int i;
                strbuf_addstr(out, plural);
                for (i = 0; i < list->nr - 1; i++)
                        strbuf_addf(out, "%s%s", i > 0 ? ", " : "", list->list[i]);
                strbuf_addf(out, " and %s", list->list[list->nr - 1]);
        }
}

static void shortlog(const char *name, unsigned char *sha1,
                struct commit *head, struct rev_info *rev, int limit,
                struct strbuf *out)
{
        int i, count = 0;
        struct commit *commit;
        struct object *branch;
        struct list subjects = { NULL, NULL, 0, 0 };
        int flags = UNINTERESTING | TREESAME | SEEN | SHOWN | ADDED;
        struct strbuf sb = STRBUF_INIT;

        branch = deref_tag(parse_object(sha1), sha1_to_hex(sha1), 40);
        if (!branch || branch->type != OBJ_COMMIT)
                return;

        setup_revisions(0, NULL, rev, NULL);
        rev->ignore_merges = 1;
        add_pending_object(rev, branch, name);
        add_pending_object(rev, &head->object, "^HEAD");
        head->object.flags |= UNINTERESTING;
        if (prepare_revision_walk(rev))
                die("revision walk setup failed");
        while ((commit = get_revision(rev)) != NULL) {
                struct pretty_print_context ctx = {0};

                /* ignore merges */
                if (commit->parents && commit->parents->next)
                        continue;

                count++;
                if (subjects.nr > limit)
                        continue;

                format_commit_message(commit, "%s", &sb, &ctx);
                strbuf_ltrim(&sb);

                if (!sb.len)
                        append_to_list(&subjects, xstrdup(sha1_to_hex(
                                                        commit->object.sha1)),
                                        NULL);
                else
                        append_to_list(&subjects, strbuf_detach(&sb, NULL),
                                        NULL);
        }

        if (count > limit)
                strbuf_addf(out, "\n* %s: (%d commits)\n", name, count);
        else
                strbuf_addf(out, "\n* %s:\n", name);

        for (i = 0; i < subjects.nr; i++)
                if (i >= limit)
                        strbuf_addf(out, "  ...\n");
                else
                        strbuf_addf(out, "  %s\n", subjects.list[i]);

        clear_commit_marks((struct commit *)branch, flags);
        clear_commit_marks(head, flags);
        free_commit_list(rev->commits);
        rev->commits = NULL;
        rev->pending.nr = 0;

        free_list(&subjects);
}

int fmt_merge_msg(int merge_summary, struct strbuf *in, struct strbuf *out) {
        int limit = 20, i = 0, pos = 0;
        char *sep = "";
        unsigned char head_sha1[20];
        const char *current_branch;

        /* get current branch */
        current_branch = resolve_ref("HEAD", head_sha1, 1, NULL);
        if (!current_branch)
                die("No current branch");
        if (!prefixcmp(current_branch, "refs/heads/"))
                current_branch += 11;

        /* get a line */
        while (pos < in->len) {
                int len;
                char *newline, *p = in->buf + pos;

                newline = strchr(p, '\n');
                len = newline ? newline - p : strlen(p);
                pos += len + !!newline;
                i++;
                p[len] = 0;
                if (handle_line(p))
                        die ("Error in line %d: %.*s", i, len, p);
        }

        if (!srcs.nr)
                return 0;

        strbuf_addstr(out, "Merge ");
        for (i = 0; i < srcs.nr; i++) {
                struct src_data *src_data = srcs.payload[i];
                const char *subsep = "";

                strbuf_addstr(out, sep);
                sep = "; ";

                if (src_data->head_status == 1) {
                        strbuf_addstr(out, srcs.list[i]);
                        continue;
                }
                if (src_data->head_status == 3) {
                        subsep = ", ";
                        strbuf_addstr(out, "HEAD");
                }
                if (src_data->branch.nr) {
                        strbuf_addstr(out, subsep);
                        subsep = ", ";
                        print_joined("branch ", "branches ", &src_data->branch,
                                        out);
                }
                if (src_data->r_branch.nr) {
                        strbuf_addstr(out, subsep);
                        subsep = ", ";
                        print_joined("remote branch ", "remote branches ",
                                        &src_data->r_branch, out);
                }
                if (src_data->tag.nr) {
                        strbuf_addstr(out, subsep);
                        subsep = ", ";
                        print_joined("tag ", "tags ", &src_data->tag, out);
                }
                if (src_data->generic.nr) {
                        strbuf_addstr(out, subsep);
                        print_joined("commit ", "commits ", &src_data->generic,
                                        out);
                }
                if (strcmp(".", srcs.list[i]))
                        strbuf_addf(out, " of %s", srcs.list[i]);
        }

        if (!strcmp("master", current_branch))
                strbuf_addch(out, '\n');
        else
                strbuf_addf(out, " into %s\n", current_branch);

        if (merge_summary) {
                struct commit *head;
                struct rev_info rev;

                head = lookup_commit(head_sha1);
                init_revisions(&rev, NULL);
                rev.commit_format = CMIT_FMT_ONELINE;
                rev.ignore_merges = 1;
                rev.limited = 1;

                for (i = 0; i < origins.nr; i++)
                        shortlog(origins.list[i], origins.payload[i],
                                        head, &rev, limit, out);
        }
        return 0;
}

int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
{
        const char *inpath = NULL;
        struct option options[] = {
                OPT_BOOLEAN(0, "log",     &merge_summary, "populate log with the shortlog"),
                OPT_BOOLEAN(0, "summary", &merge_summary, "alias for --log"),
                OPT_FILENAME('F', "file", &inpath, "file to read from"),
                OPT_END()
        };

        FILE *in = stdin;
        struct strbuf input = STRBUF_INIT, output = STRBUF_INIT;
        int ret;

        git_config(fmt_merge_msg_config, NULL);
        argc = parse_options(argc, argv, prefix, options, fmt_merge_msg_usage,
                             0);
        if (argc > 0)
                usage_with_options(fmt_merge_msg_usage, options);

        if (inpath && strcmp(inpath, "-")) {
                in = fopen(inpath, "r");
                if (!in)
                        die_errno("cannot open '%s'", inpath);
        }

        if (strbuf_read(&input, fileno(in), 0) < 0)
                die_errno("could not read input file");
        ret = fmt_merge_msg(merge_summary, &input, &output);
        if (ret)
                return ret;
        write_in_full(STDOUT_FILENO, output.buf, output.len);
        return 0;
}